Photographic objective having three meniscus shaped elements air spaced apart



SEARCH ROC H. EISMANN ET AL PHOTOGRAPHIC OBJECTIVE HAVING THREE MENI 2,780,138 scus Feb. 5, 1957 United States Patent 2,780,138 PHOTOGRAPHIC OBJECTIVE HAVING THREE wRl SrCUS SHAPED ELEMENTS AIR SPACED Helmnt Eismann, Heidenheim (Brenz), Walter Jahn, 5 Lenses Konigsbronn, and Giinther Lange, Heidenheim (Brenz), Germany, assignors to Carl Zeiss, Heidenheim (Brenz), Wurttemberg, Germany Application March 15, 1955, Serial No. 494,354 Claims priority, application Germany April 5, 1954 2 Claims. (CI. 88-57) the two last mentioned elements turn their concave sides towards one another and each consists of two cemented together lenses of opposite refractive power in such a way, that the two cemented surfaces turn their convex sides towards one another. The objectives in accordance with the invention are characterized by a well-balanced state of correction, which comes about through the working together of the following characteristics: the cemented surface in the middle element has dispersive and the cemented surface in the rear element collective action, the central thickness of each of the cemented elements amounts to less than the 0.2-fold of the focal length 1 of the objective, the refractive index of the lens of the cemented middle element turned towards the rear ele-' ment is greater than 1.640, and finally still the following conditions are fulfilled:

whereby the over-all length of the objective is designated with L and the radii of the respective surfaces with r.

Two objectives with the characteristics of the present invention are represented in Figures 1 and 2 of the annexed illustrations. In their construction they correspond to the numerical values specified in the two following tables. These two objectives form part of the invention with these numerical values, of which the surface refractive powers (An/r) each deviate at most by :0.5/f and of which the thicknesses andair distances each deviate at most by 10.057 from the values to be taken from the following tables:

Example I (Fig. 1)

Example II (Fig. 2)

Thlcknesses Radil and m V (A'n/r) Distances r1=+0. 482477 +1. 381868] L; d1=0. 05160 1.66672 48.4 f

n= 7 Lu d1=0. 03511 1.60562 43.9

n= --1. 44035 -0. 064797/f L ds=0. 03900 1. 69895 30.1

n= --0. 786994 -0. 756089/1 Ln"--. d4=0. 01340 1. 59551 30. 2

r1-+0. 283286 +0. 451522/j Lv ds=0.08283 1.72342 38.23

In both examples L: to Lv are the single elements, and the Roman numerals refer to these elements starting with the front side, r1 to rs are the radii of curvature of the refractive surfaces from front to rear as indicated in the drawing, the and signs refer respectively to surfaces convex and concave to the front, d1 to d5 are the axial thicknesses of the elements, L is the axial overall length of the objective, I1 is the air spacing between elements L: and Lu and la is the air spacingbetween elements Lin and Lrv, n4 is the index of refraction with reference to the d-line of the spectrum, V is the dispersive index, and An/r is the refractive power of the respective surface.

We claim:

1. Photographic objective consisting of three meniscusshaped elements, separated from one another by air spaces, the first being a simple collective front element turning its convex side towards the object to. be photographed, the second being a dispersive middle element, and the third being a collective rear element, the two last mentioned elements turning their concave sides towards one another and each said last mentioned elements consisting of two cemented together lenses of opposite refractive power the two cemented surfaces turning their convex sides towards one another, the cemented surface in the said middle element having dispersiveand the cemented surface in the said rear element having collective action, the central thickness of each of the said cemented elements amounting to less than the 0.2-fold of the focal length 1 of the objective, and the refractive index of the lens of the said cemented middle element turned totwards the rear element being greater than 1.640, and

finally the following further conditions being fulfilled:

distances each at most by 10.051 from the values to be taken from the following numerical example:

where Lr to Lv are the single elements, and the Roman numerals refer to these elements starting with the front side, n to re are the radii of curvature of the refractive surfaces from front to rear as indicated in the drawing, the and signs refer respectively to surfaces convex and concave to the front, d1 to da are the axial thicknesses of the elements, L is the axial overall length of the objective, [1 is the air spacing between elements L1 and Lu and la is the air spacing between elements Lu: and

Lrv, m1 is the index of refraction with reference to the d-line of the spectrum, V is the dispersive index, and An/r is the refractive power of the respective surface.

2. Photographic objective consisting of three meniscusshaped elements, separated from one another by air spaces, the first being a simple'collective front element turning its convex side towards the object to be photographed, the second being a dispersive middle element, and the third being a collective rear element, the two last mentioned elements turning their concave sides towards one another and each said last mentioned elements consisting of two cemented together lenses of opposite refractive power the two cemented surfaces turning their convex sides towards one another, the cemented surface in the said middle element having dispersive and the cemented surface in the said rear element having collective action, the central thickness of each of the said cemented elements amounting to less than the 0.2-fold of the focal length f of the objective, and the refractive index of the lens of the said cemented middle element, turned towards the rear element being greater than 1.640,

and finally following further conditions being fulfilled:

and in which the surface refractive powers (An/r) each deviate at most by iOJ/f, and the thicknesses and the air distances each at most by i0.05-f from the values to be taken from the following numerical example:

Lenses Radii Thieknesses m V (An/r) and Distances r1= +0.482477'f +1.381868/ L1..- d1=0.05160-f 1.66672 48. 4 f

r =+1.24730'f --0.534531/f +0 241815 1' 11-00013 +2 5044 6/ Ts== 7 Lu" dr=0.0851l'f 1.60562 43. 9 f r4= -l.44035- f --0.064797/f Lm. da=0.03900-f 1.69895 30. 1

r5=+0.l78737-f 3.910494/)' l.'|=0.11460-f To= 0.786994-f -0.756689/f Lrv... |i4=0.0l340-f 1.59551 39. 2

r1=+0.283286-f +0.451522/f Lv ds=0.08283-f 1.72342 38. 23

ra= 0.616205-f +1.190237/f where L: to Lv are the single elements, and the Roman numerals refer to these elements starting with the front side, n to re are the radii of curvature of the refractive surfaces from front to rear as indicated in the drawing, the and signs refer respectively to surfaces convex and concave to the front, :11 to da are the axial thicknesses of the elements, L is the axial overall length of the objective, [1 is the air spacing between elements L1 and Lu and la is the air spacing between elements Lm and Lrv, na is the index of refraction with reference to the d-line of the spectrum, V is the dispersive index, and An/r is the refractive power of the respective surface.

References Cited in the file of this patent UNITED STATES PATENTS 1,880,394 Altman Oct. 4, 1932 1,939,098 Berek Dec. 12, 1933 1,998,704 Bertele Apr. 23, 1935 2,186,622 Bertele Ian. 9, 1940 2,562,012 Bertele July 24, 1951 2,623,434 Bechtold Dec. 30, 1952 

